(a) Technical Field
The present invention relates to a manifold block for a fuel cell stack. More particularly, the present invention relates to a manifold block for a fuel cell, which improves the electrical insulation of a coolant flow channel in an internal flow channel.
(b) Background Art
A fuel cell is a stand alone electrical generation system that does not convert the chemical energy from fuel into heat via combustion, but instead electrochemically converts the chemical energy directly into electrical energy in a fuel cell stack or module. At present, one of the most attractive fuel cells for a vehicle is a polymer electrolyte membrane fuel cell (PEMFC), which has the highest power density among the fuel cell options on the market.
The fuel cell stack included in the PEMFC includes a membrane electrode assembly (MEA), a gas diffusion layer (GDL), a gasket, a sealing member, and a separator. The MEA includes a polymer electrolyte membrane through which hydrogen ions are transported. An electrode/catalyst layer, in which an electrochemical reaction takes place, is disposed on each of both sides of the polymer electrolyte membrane. The GDL uniformly diffuses reactant gases and transmit generated electricity. The gasket provides an appropriate airtight seal for the reactant gases and coolant. The sealing member provides an appropriate bonding pressure, and the separator supports the MEA and GDL, collects and transmits generated electricity, transmits reactant gases, transmits and removes reaction products, and transmits coolant to remove reaction heat, etc.
A fuel cell stack also includes a manifold block for forming an inlet flow channel and an outlet flow channel of the fuel cell stack. The manifold block acts as an interface member which allows gas and coolant before and after the reaction to flow in and out of the fuel cell stack respectively.
The manifold block has a long and complex internal flow channel through which gas and coolant passes. When a plurality of stack modules are mounted to a fuel cell vehicle, the manifold block attached to the outside of the stack module serves to uniformly supply reactant gases (air and hydrogen) and coolant to each stack module. For example, the manifold block is typically manufactured via aluminum die-casting and then forms an insulating coating on a coolant flow channel.
FIG. 1 is a cross-sectional view illustrating a conventional manifold block with a coolant flow channel that is connected to a stack module, taken along the coolant flow channel 11. As shown in FIG. 1, an end plate 31 is assembled to the outermost end of a fuel cell stack 30, and a manifold block 10 is attached to the outside of the end plate 31 with a gasket 32 interposed therebetween.
An interface unit 14, through which coolant is introduced, is connected to one side of the manifold block 10 such that the coolant introduced through the interface unit 14 passes through the coolant flow field 11 in the manifold block 10 and is supplied to the stack module 30 and the coolant discharged from the stack module 30 is discharged to the outside through the interface unit 14. The interface unit 14 may be, for example, made of plastic. In FIG. 1, a coolant flow channel for discharging the coolant exiting from the stack module 30 to the outside, and a corresponding interface unit for discharging the coolant are not shown.
In the manifold block 10 shown in FIG. 1, the coolant flow channel 11 is in the form of a straight line bent at a predetermined angle, and the coolant is filled therein at all times. When coolant is filled in the coolant flow field 11 of the manifold block 10, high-voltage electricity generated in the stack module 30 may travel to the outside (e.g., a chassis of the vehicle) through the coolant in the aluminum manifold block. This uncontained electricity may cause an electrical shock to a driver or individual working on the vehicle. Accordingly, an insulating coating (e.g., ceramic coating, epoxy coating, Teflon coating, etc.) is often applied to the entire coolant flow channel 11 of the manifold block 10.
The manifold block 10 shown in FIG. 1 provides a simple design and a sufficient size, for the coolant flow channel, thus reducing the differential pressure therein. However, the quality of coating quality changes significantly based on the operational environment during the insulating coating process, and the surface roughness becomes worsens due to agglomeration of the coating, which is very problematic. Moreover, the insulation performance is satisfactory initially but degrades over time, and after the insulating coating is destroyed, electrical corrosion begins to occur, which is also problematic.
In an effort to solve these problems, as shown in FIG. 2, a manifold block 10 in which a separate insulating member is mounted to a coolant flow channel has been disclosed. As shown in FIG. 2, an insulating member 21 having the same shape as a coolant flow field 11 is put on a conventional manifold block 10, and a bisected plastic insulating cover 23 for fixing and protecting the insulating member 212 is inserted into both sides of the flow field, thus ensuring insulation of the coolant flow field and, at the same time, eliminating the insulating coating process which is additionally performed in the existing manifold block.
However, the conventional manifold block 10 has the following problems. Additional parts such as the insulating member 21, the insulating cover 23, etc. are used, which increases the development and manufacturing costs. Moreover, the insulating cover 23 in the flow field may be damaged, which blocks the coolant channel, and the joint of the bisected insulating cover may adversely affect the coolant flow.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.